Typically, transmitted signals are collected by a receiver and processed during predetermined time intervals called dwells. The processing of signals received during a previous dwell occurs during a subsequent dwell. An inter-dwell period exists between dwells to allow for the reconfiguration of data processing circuits and other hardware in response to the processed data of the most recent dwell. Any processing of received signals or collecting of received signals is typically halted during this inter-dwell period.
There are several electronic support measure (ESM) analyses that must employ dwells to isolate emitter signals in both frequency and amplitude. These include Scan Modulation Analysis (SMA), Specific Emitter ID (SEI) and certain forms of Mode Change Detection (MCD). Typically, the emitter signals are intercepted in a wide instantaneous frequency (IF) bandwidth dwell and the analysis is performed in a narrow IF bandwidth dwell. With the switch in bandwidth comes an increase in sensitivity, requiring the prediction of the narrowband IF signal amplitude derived from the wide IF amplitude intercepted signal. ESM receivers typically perform this task by table look up, setting hardware and software detection thresholds accordingly. This works well when hardware specifications tightly control sensitivity.
However, systems that are less stringently specified typically rely on dynamic calibration to optimize sensitivity independently for each bandwidth. These systems may exhibit fluctuations in sensitivity and sensitivity deltas. In these cases, a strict table look up may over or under compensate, leading to either too much signal being detected or not detecting the signal at all (See FIG. 5).